Material
Specifications
Part 1

ASTM
D 2000

Specifications
for physical properties of elastomeric seals can be very general or extremely
specific in nature. Probably the most common general classification system
is ASTM D 2000 “Standard Classification System for Rubber Products
in Automotive Applications.” The purpose of this classification
system is to aid in the selection of practical rubber products for specific
environments. It also provides a “line call-out” designation
for the specification of materials.

Rubber materials
are designated by type (heat resistance) and class (oil resistance). The
heat resistance of an elastomer is based on changes in tensile strength
of not more than ± 30%, elongation of not more than –50%,
and hardness of not more than ±15 points after 70 hours of aging
at the specified temperature. The oil resistance is based on the volume
swell of an elastomer after a 70-hour immersion in ASTM Oil No. 3.

An example
of the general classification positioning of different elastomers is shown
in the chart below.

The line
call-out, or specification, contains appropriate information for testing
and designation for a sealing elastomer. The example shown illustrates
a typical line call-out: